The long range objective of this research proposal is to gain further insight, in molecular terms, into the structure and translation of two mRNA species: one coding for the synthesis of rhodopsin, the membrane-associated protein that is the primary photoreceptor molecule in all vertebrate species; the other, the mRNA molecules coding for the Alpha ad Beta subunits of tubulin, the structural protein of the microtubules that form the basis of a number of organelles such as the mitotic spindle, eucaryotic flagellar, nerve-cell processes and cytoskeletal elements. The importance of understanding the biosynthesis of rhodopsin stems in part from its function as the primary photoreceptor and in part from its role as a protein inserted with a specific polarity into membranes. A knowledge of tubulin biosynthesis is important because little is known about the genomic organization that determines the regulation and expression of intracellular structural proteins. The following types of investigation are proposed: 1) Isolation of the mRNAs that code for rhodopsin and the Alpha and Beta subunits of tubulin. 2) Characterization of the products produced on translation of isolated mRNAs in a cell-free system. 3) Chemical analysis of the isolated mRNAs, particularly with respect to the untranslated regions. 4) Determination of the sites of synthesis of rhodopsin and tubulin within the cell. 5) Estimation of the number of genes for rhodopsin and tubulin, and possible localization of tubulin genes on the Drosophila polytene chromosome.